Case Study Of Designing A Special Purpose Machine

NOVATEUR PUBLICATIONS INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT] VOLUME 1, ISSUE 1 NOVNOV-2014 Case Study of Designing a Special Purpose Machine Prof. Prasad Bapat Department of Mechanical, Mumbai University / MPCOE, Velneeshwar, India prasad.rbgi@gmail.com Prof. J.Y. Acharya Department of Mechanical, Mumbai University / RSCOE, Chiplun, India ABSTRACT Special purpose machine tools are designed and manufactured for specific jobs and such never produced in bulk such machines are finding increasing use in industries the techniques for designing such machine would obviously be quite different from those used for mass produced machine. A very keen judgment is essential for success of such machines. This paper explains a case study of designing special purpose machine and manufactured at ABC Company which found beneficial in increasing production quantity & reducing manpower. KEYWORDS: - SPM, LOCUS CLEARANCE, MACHINE HEAD, CASTINGS BLOCKS INTRODUCTION TO SPECIAL PURPOSE MACHINE Broadly the special purpose machine tools could be classified as those in which jobs remain fixed in one position and those in which job moves from one station to other (Transfer machine).In first case the machine may perform either only one operation or more .In the second case, the product may be either moving continuously (as in the case of spraying, polishing, sanding etc) or intermittently (the most usual case in machining operation). Rotary intermittently motion transfer machine is very popular production machine and is described in brief bellow. Such a machine comprises a turret on whole periphery several heads are mounted to receive and locate the components for working. The turret rotates intermittently about its central axis which is provided with fine and sophisticated mechanisms to control its motion so that before stopping it is properly decelerated and desired positioning accuracy is attained at stationary positions around the usually mounted on a table are the several tools and unit which perform the machining operation. It is essential that all movements be completely synchronized in order to obtain desired product it is essential that all tools and units must have completed their operation and be withdrawn clear of the turret before it starts to index similarly the turret index precisely and come to rest before tools and units begin their work. MECHANISMS: There are a variety of index machines and this need to be selected properly to suit the given requirement. A versatile indexing unit used in presses, drilling machines has number of indexes, speed of index and dwell time which can be readily changed in this mechanism. It operates by fluid power and uses ratchet and pawl mechanism. DESIGN OF SPECIAL PURPOSE MACHINE (SPM):PROBLEM DEFINITION:- The company was using various types of milling machines like horizontal milling machine, vertical milling machine angular milling machine and HMCs the company designs and manufactures the special purpose machines needed by it in house and intended to do the same in case of milling operations. The machine will be used in milling in4 cylinder 40HP engine block of Tata motor. The problem associated with the machine was that it was a tedious and time consuming part to mill the locus clearance in the engine block on three different machines. Also the most difficult task was to mill the portion in locus type pattern. So the machine is meant to be a rough milling machine, 1 Page

NOVATEUR PUBLICATIONS INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT] VOLUME 1, ISSUE 1 NOVNOV-2014 the clearance produced by it was not accurate and vibration produced was creating problem to the operator for achieving the required accuracy. Also the time taken for milling operation was quite large and there was a scope in reduction of machining time so by reducing these two parameters of vibration and machining time more output could be achieved. The above problem could be solved by designing a machine having a hydraulic type spindle having milling tool such that angular or rotational motion can be achieved. Though it will increase the cost of designing the new machine it will be nullified by reduction in machining time. Fig. Actual working model of SPM designed and manufactured. DESIGN PROCEDURE FOLLOWED:- 1) 2) 3) 4) 5) 6) 7) 8) 9) Design of Spindle Unit Design of Spindle Shaft Selection of Bearing Design of Gear Box Selection of Lubricants Sealing of Rolling Bearing Assembly procedure of spindle unit Assembly procedure for Gear Box Inspection after Assembly Inputs of Machine: SR. NO. ENTITIES Diameter of Locus clearance bore as cast (D) 30mm,to be machined 1 Cutting speed (V) 40m/min 2 3 4 5 6 7 8 9 Revolutions per minute (n): We Know, v πDn/1000 40 π 30 n/ 1000 n 40 1000/π 30 n 424.41rpm Feed (f) 0.1 mm/tooth Feed per minute (fm) f n 42.44 mm/min Depth of cut (t) 5 mm Metal removal rate (Q) f t v 20 cm3 /min Approach Angle (x0) 900 Average chip thickness (as) f sin x0 0.1 mm 2 P age

NOVATEUR PUBLICATIONS INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT] VOLUME 1, ISSUE 1 NOVNOV-2014 Unit power (U) 31 KW/ cm3/min Correction factor for flank wear (kh) 1.18 Side rack angleγ0 00 Correction factor for rake angle (Kγ) Kγ 1.13 Power at the spindle (N) U kh Kγ Q 0.826 kw Efficiency of transmission (E) 95% Power of the motor (Nel) N/E 0.8694 kw Tangential cutting force ( pz) 6120 N/V 1239.344N (1 kgf 9.80665 N) Torque at the spindle (Ts) 975 N/n 18.6088 103 N-mm 10 11 12 13 14 15 16 17 18 JUSTIFICATION OF NEW SPM LOCUS CLEARANCE MILLING FOR OLD MILLING MACHINE Sr.No. Parameters Quantity 1 2 Working hours/shift No. of working days in week 8 6 3 4 No. of operators Working days per month 3 25 STANDARD TIME PER UNIT PER SHIFT PER MONTH Sr.No. 1 2 3 Parameters Machine time Operator time Total time/unit Min. 12 3 15 Calculations Machine time 12/0.85 14.11 Operator time 3 min. Total time/unit 17.11 No. of units produced/shift/month 8 60 25/17.11 701 units. No. of units produced per months 701 3 (Three sifts per day) 2103 units. FOR NEW MILLING MACHINE Sr.No. 1 Parameters Working hours/shift Quantity 8 2 3 4 No. of working days in week No. of operators Working days per month 6 1 25 3 Page

NOVATEUR PUBLICATIONS INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT] VOLUME 1, ISSUE 1 NOV NOV--2014 STANDARD TIME PER UNIT PER SHIFT PERMONTH Sr.No. Parameters Min. 1 Machine time 4.12 2 3 Operator time Total time/unit 0.45 5.3 Calculations Machine time 4.12/0.95 4.33 Operator time 1 min. Total time/unit 5.33 No. of units produced/shift/month 8 60 25/5.33 2264 2264 units No. of units produced per months 2264 3 (Three sifts per day) 6792 units Operators Opn Machine Total No. of No. Cycle time Components Per shift per month In min Machining cost per unit Machining cost per month 1 2 20 15 1, 01,880 42,060 OLDSPM NEWSPM 17.11 5.5 2103 6792 3 1 Table No.1 Justification of new SPM locus clearance milling Total cost saving per month : 59,820/- Total cost saving per year : 7, 17,840/- 5.5 Total cycle time in minutes 17.11 0 5 NEW SPM 10 15 OLD SPM 20 Fig. 2 Graphical representation of the data obtained. 4 P age

NOVATEUR PUBLICATIONS INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT] VOLUME 1, ISSUE 1 NOV NOV--2014 6792 No. of components per months 2103 0 NEW SPM 2000 4000 6000 8000 OLD SPM Fig. 3 Graphical representation of the data obtained. 1 Operators per shift 3 0 1 NEW SPM 2 3 OLD SPM 4 Fig. 4 Graphical representation of the data obtained. 15 Machining cost per unit 20 0 10 NEW SPM 20 OLD SPM 30 Fig. 5 Graphical representation of the data obtained. 5 P age

NOVATEUR PUBLICATIONS INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT] VOLUME 1, ISSUE 1 NOV NOV--2014 42060 Machining cost per month 101880 0 40000 80000 NEW SPM OLD SPM 120000 Fig. 6 Graphical representation of the data obtained. CONCLUSION From the overall procedure we followed in designing of the spindle unit and gear box , we conclude that design is safe , accordingly the design could be brought into practice while designing we have successive in keeping the cost factor to minimum total net savings per year after new SPM is Rs.7,17,840. Previously for the locus clearance machine three men were utilized for each machine all operation will be done on one SPM and for that one man will be required therefore saving in manpower m will be 3-1 1 2 men saved per day also there will be saving in space, power consumed, wages paid, handling and machining time etc.this will result into increase productivity and profit. The company can machine additional unit produced per year and m meet the customers demand. References [1]Machine Machine Tool Design Handbook: Central Machine Tool Institute, Bangalore. (Tata McGraw-Hill Hill Publishing Company Ltd. Year 2002) [2]Design Design of Machine Elements: V. B. Bhandari (Tata McGraw-Hill Hill Publishing Company Ltd. Year 2002) [3]Machine Machine Design: R.S. Khurmi & J.K. Gupta (S. Chand Publication Ltd. Year 1998) [4]Production Production Technology: R.K. Jain S.C. Gupta (Khanna Publications, New Delhi Year 1982) 6 P age

DESIGN OF SPECIAL PURPOSE MACHINE (SPM):- PROBLEM DEFINITION:- The company was using various types of milling machines like horizontal milling machine, vertical milling machine angular milling machine and HMCs the company designs and manufactures the special purpose machines needed by it in house and intended to do the same in case of milling